Glutamic acid recovery



Sept. 13, 1960 H. l.. FIKE 2,952,705

GLUTAMIC ACID RECOVERY Filed June 12, 1958 United States arent dice GLUTAMIC ACID RECOVERY Harold L. Fike, Chicago, Ill., assignor to International Minerals & Chemical Corporation, a corporation of New York This invention relates to the recovery of glutamic acid from sugar beet waste liquors. More particularly, it relates to an improvement in the so-called coneutralization process for recovering glutamic acid from Steffens filtrate and other forms of sugar beet waste liquors.

Glutamic acid is conveniently recovered from sugar beet waste liquors by subjecting the liquors to hydrolysis, concentrating and desalting, and crystallizing the glutamic acid at the isoelectric point thereof, around pH 3.2. Hydrolysis under acid conditions offers the advantage of eecting more nearly complete conversion of the glutamic acid precursor compounds contained in the liquors, but is higher in reagent costs and tends to produce severe corrosion of process equipment; for these reasons alkaline hydrolysis has been adopted almost eX- clusively by the art. Alkaline hydrolysis is usually carried out at high pH levels in the range of about l2 or above; and inasmuch as the crystallization of the resulting glutamic acid must be carried out under acidic conditions, it is necessary to neutralize all of the alkali contained in the hydrolyzate before crystallization can be carried out. Large quantities of reagents are thus required for the initial hydrolysis and for the neutralization and acidification, and the process liquor thereby becomes heavily loaded with inorganic salts, which must be removed at least in part. To minimize this difculty, the so-called co-neutralization process employs both acid and alkaline hydrolysis on separate portions of sugar beet waste liquors, then co-neutralizes the hydrolyzates with each other to the desired pH levels for desalting and for glutamic acid crystallization. Despite its advantages, however, the co-neutralization process has never been employed on a commercial scale because it has required that the partially neutralized alkaline hydrolyzate be concentrated to impracticably high solids levels around 90% by weight, or has required that one or more process streams be concentrated under highly corrosive pH conditions or under conditions promoting the reversion of glutamic acid to pyrrolidonecarboxylic acid. The present invention is a means for avoiding or minimizing these difficulties.

An object of the invention is to provide an improved co-'neutralization process for recovering glutamic acid from sugar beet Waste liquors, in particular from Steffens filtrate.

Another object is to avoid the concentration of process liquors to impracticably high solids levels Vduring the recovery of glutamic acid from sugar beet waste liquors.

Another object is to avoid the need for concentrating highly acidied solutions in the recovery of glutamic acid from sugar beet waste liquors.

Another object is to avoid the need for concentrating process liquors under pH conditions conducive to the 'reversion of glutamic acid to pyrrolidonecarboxylic acid.

Other objects of the invention will be apparent In the prior-art co-neutralization process, a major difficulty lies in the problem of co-neutralizing the partially acidiiied and desalted alkaline hydrolyzate to pH 3.2 for glutamic acid crystallization, While simultaneously arriving at a solids concentration sufficiently high to permit effective crystallization of the glutamic acid. This has been difficult, because the acid hydrolyzate ordinarily has a solids concentration of only about 60% by Weight, and owing to this factor it has been necessary to carry the concentration of the desalted liquor -to about 90% solids by weight prior to the final co-neutralization to pH 3.2. Such an extreme degree of concentration is exceedingly diificult in practice. Alternatively, it has been necessary to concentrate the acid hydrolyzate itself vto 65% solids or higher, which is diflicult because of the corrosive nature of the acid hydrolyzate.

The present invention avoids these diiculties in the following manner. The acid hydrolysis is carried out in the presence of hydrochloric acid in a known manner. The resulting hydrolyzate is cooled and agitated gently to permit betaine hydrochloride and glutamic acid hydrochloride to crystallize therefrom. The acid values in the acid hydrolyzate are thereby concentrated in part into the crystallized material. The resulting crystals, ordinarily with a portion of the liquid phase, are used to carry out the adjustment of the desalted hydrolyzate to pH 3.2, while the remainder of the liquid phase is used for the initial pH adjustment of the alkaline hydrolyzate prior to desalting. By proceeding in this manner, the acid values in the acid hydrolyzate are fractionated and concentrated into one portion thereof which can be used for iinal adjustment of a partially desalted hydrolyzate to around pH 3.2 without causing material dilution of the latter. It thereby becomes unnecessary to concentrate the partially desalted hydrolyzate, prior to or after desalting, to excessively high solids levels, as required heretofore in the art; and the mixture of hydrolyzate streams obtained at pH 3.2 is immediately ready for crystallization of glutamic acid therefrom.

In one embodiment of the invention, concentrated Steffens filtrate having a solids content between about 55 and about by weight, preferably around 65%, is subjected to hydrolysis in the presence of hydrochloric acid. The hydrolyzate is preferably filtered to remove humin substances, and is then allowed to stand at ordinary or somewhat reduced temperatures with gentle stirring to permit crystallization of betaine hydrochloride and glutarnic acid hydrochloride. The resulting solids are settled, centrifuged, or filtered, and the acid hydrolyzate is separated into two portions, one portion containing the solid phase and comprising about 40 to about 47.5% by volume of the total hydrolyzate, While the other portion comprises the remainder of the liquid phase. Another portion of Steffens filtrate is hydrolyzed with alkali under conventional conditions, and the alkaline hydrolyzate is co-neutralized With the liquid acid hydrolyzate fraction in a proportion to reach a pH between about 4 and about 6, preferably between about 4.5 and about 5.5. The humin substances from the acid hydrolyzate may be returned to the process at this point if desired, to recover the glutamic acid values therein. insoluble material is separated from the mixture, and the liquid phase is concentrated and partially desalted, then co-neutralized to a pH around 3.2 with the acid hydrolyzate fraction containing betaine hydrochloride and glutamic acid hydrochloride, at which point glutamic acid crystallizes readily `from the solution.

Prior to the acid hydrolysis step of the process, concentrated Steifens `filtrate is preferably rst treated with a sucient quantity of sulfuric acid to precipitate glaserite and certain other inorganic salts. The treated liquor is then commingled with hydrogen chloride or concentrated hydrochloric acid in a proportion to provide an. 1:1@ 991th 3 centration around Y7 to 16% by weight, preferably between about 10 and about 14% by weight. At the same time the solids content of the liquor should remain above about 55 by weight, and should preferably be around 60 to Y65% by weight. Y The acidified liquor is subjected to hydrolysis by heating at la temperature between about 10U-and about .125 C. for a period of around 1A to 4 hours, preferably at about 110 C. for -about 1.5 hours. The resulting hydrolyzate contains a small proportion of burnin materials which would be undesirable in the glutamic acid crystallization step. For this reason, it is preferred to remove such materials, suitably by filtration, from the acid hydrolyzate prior to further treatment. The humin materials thus separated contain a small proportion of glutamic `acid values Vwhich can be recovered by returning the humin to the process stream as set forth below. The humin-free acid hydrolyzate is cooled to ordinary or somewhat reduced temperatures, and is gently agitated for a period of aboutr4 to about 48 hours, preferably around 24 hours, to permit betaine hydrochloride and glutamic acid hydrochloride to crystallize therefrom. The resulting crystals can be removed completely from the liquid phase if desired by filtration, centrifugation, orV the like, then used in conjunction with a portion of the acid hydrolyzate liquid phase to effect co-neutralization of partially desalted hydrolyzate to pH 3.2. Preferably, however, the betaine hydrochloride and glutamic acid hydrochloride are merely allowed to settle to the bottom ofthe crystallization vessel, and the supernatant liquor is decanted off to the extent desired, leaving a slurry of betaine hydrochloride and glutamic acid hydrochloride in acid hydrolyzate, suitable for the co-neutralization to pH 3.2. The said slurry will ordinarily comprise between about 40 to about 47.5% by volume of the total acid hydrolyzate in order toprovide the required acid and solids content for the pH 3.2 12o-neutralization ywhile leaving a liquid volume containing the required amount of acid for the initial co-neutralization of the alkaline hydrolyzate.

InY the Valkaline hydrolysis, concentrated Steffens filtrate is alkalized with sodium hydroxide, potassium hydroxide, or other strong alkali, and is hydrolyzed by heating under conventional conditions. Ordinarily less than about 10% by weight (e.g., 4 to 8%) of alkali is employed, and the hydrolysis is completed at about 60 to about 100 C. in about 1 to about 4 hours (e.g., 21A hours at 85 C.). The alkaline hydrolyzate is then co-neutralized with the `major (i.e., liquid-phase) portion of the acid hydrolyzate, the humins being added thereto if desired, and the quantities being adjusted to reach a pH between about 4 and about 6, preferably about 4.5 to about 5.5. The resulting mixture is commingled with an aqueous solution of tannin or alkali lignin to precipitate the humins 'and other yorganic impurities, which are removed by filtration. The liquid phase'is concentrated to between about 65 and about 85% by Weight of dry solids, and the resulting crop of inorganic salts is separated at a tempera- Vture between about 65 and labout 85 C. The desalted solution is co-neutralized to a pH around 3.2 with Vthe minor portion ofthe acidV hydrolyzate, containing the betaine hydrochloride and the glutamic acid hydrochloride. The co-neutralized material is sufficiently high in solids concentration to permitefiective crystallization of glutamic acid therefrom, which is carried out by cooling, seeding if desired, and holding at ordinary or somewhat reduced` temperature for l to Ydays or longer, until crys-V tal growth has substantially ceased. The glutamic acid VVis, separated from the resulting slurry by centrifugation,

`A. sugarv'beet Waste liquor obtained ,fromV the Steffens process fortreating sugarjbeet molasses (1,7 107pounds l total weight, containing 1,000 pounds total dry solids comprising 165 pounds of glutamic acid values calculated as monosodium glutamate, hereinafter refer-red to as monosodium glutamate equivalen or MSGE) is concentrated to about 65% solids by Weight. YSulfuric acid (267 pounds of 95% H2304) is added to give a pH of about 2.0, the temperature being meanwhile held below y about 70 C. in order to minimize hydrolysis of glutamic acid precursors at this point, with consequent loss of glutamic acid values Ywith the inorganic salts precipitated by the acid. The acidified liquor is cooled to around 25 C., and inorganic sulfate salts (352 pounds of dry solids, 4 pounds MSGE) A comprising predominantly, glaserite (Na2SO4-3K2SO4) are crystallized and separated therefrom. This separation of salts is conveniently carried out by use of a filter press, basket centrifuge, or the like. The salts are washed with 2278 pounds of water, and the washings are channeled to incoming sugar beet waste liquor.

The salt-depleted liquoris then hydrolyzed under -acid conditions.l Concentrated hydrochloric acid (674 pounds of 33% HC1) is added to a pH around O, :and the hydrolysis is carried out by heating at reflux temperature (around 108 C.) for about 1.5 hours.

The resulting hydrolyzate is cooled to around 30 C. and filtered to remove humins, and the clear filtrate is allowed to stand at about '25 C. for 24 hours with gentle stirring. During this time betaine hydrochloride and glutamic acid hydrochloride crystallize therefrom, and are allowed to settle to the bottom of the crystallization vessel. A liquid fraction comprising about 55% of the total volume is ydecanted, leaving `a slurry fraction comprising about 45% of the total volume and including the crystallized solids. The slurry fraction contains about 65 of the total acidity as HCl.

An equal quantity of the Steffens filtrate (1,710 pounds total weight, containing 1,000 pounds total dry solids comprising 165 pounds MSGE) is similarly concentrated, then subjectedV to Valkaline hydrolysis. For this purpose 235 pounds of aqueous 50% sodium hydroxide are added thereto to produce a pH of about 13, and the mixture is heated at a temperature of about C. for about 21A hours. The alkaline hydrolyzate is cooled to about 30 C. and combined with the liquid fraction of the acid hydrolyzate, and also with the humins removed from the acid hydrolyzate, the resulting pH being about 5.1. Organic impurities therein are precipitated by adding 100 pounds of aqueous 10% tannin solution. The resulting humintannin solids are filtered off, washed with 342 pounds of aqueous 5% sodium chloride solution, and discarded. The humin-tannin solid phase generally contains about pounds of `dry solids, and is substantially free from monosodium glutamate equivalent. Y

The purified liquid is nextsubjected to concentration under reduced pressure to approximately 80% solids content. During this operationa large proportion of the inorganic materials contained therein are precipitated. These materials are filtered off at about 60 C., washed With 137 pounds of water, and rejected. The inorganic Vcake contains about 340 pounds of dry solids, including one pound of MSVGE; The concentrated, ltered solution is adjusted to pH 3.2. by admixture with the slurry fraction of the acid hydrolyzate. The adjusted solution is cooled to la'temperature4 around 20 C., seeded with a small quantity of glutamic acid crystals, and allowed to stand with gentle stirring for about 5 days to allow crystallization of glutamic acid to reach substantial completion. From the resulting slurry is 'centrifuged crude glutamic acid Weighing 750 pounds, Wet basis, and containing 275 kpounds'of MSGE. The' end liquor weighs 1938 pounds and contains 1,300 pounds of Vdry solids, including 56 pounds of MSGE. While the nvention'has Ybeen described by specific reference to Steffens ltrate, the underlying process and the present improvement therein are broadly applicable to the treatment of liquors containing glutamic acid-mother substances, including sugar beet waste liquors in general, such as thin barium iiltrate; fermentation residues thereof, such as vinasse and schlempe; and mixtures thereof. One stock (e.g., Steffens ltrate) can advantageously be employed for alkaline hydrolysis and a dilferent stock (e.g., vinasse) for acid hydrolysis. Likewise, while the invention has been described in connection with a detailed co-neutralization process, employing both acid and alkaline hydrolysis of starting material, it is also novel and useful in connection with a process employing acid hydrolysis alone with simple addition of alkali to the major portion of the acid hydrolyzate, as dened above, to effect a rst pH adjustment to around 4-6, then making the iinal adjustment to around pH 3.2 with the minor portion of the acid hydrolyzate. Other modications and equivalents of the invention will be apparent to those skilled in the art from the foregoing description.

In accordance with the foregoing description, the following claims particularly point out and distinctly claim the subject matter of the present invention.

I claim:

1. In a co-neutralization process for recovering glutamic acid from sugar beet waste liquors, the improvement which comprises crystallizing betaine hydrochloride and glutamic acid hydrochloride from hydrochloric acid hydrolyzate of a concentrated sugar beet waste liquor, separating the resulting slurry into a minor fraction containing the crystallized solids and a major fraction substantially free from crystallized solids, combining the major fraction with alkaline hydrolyzate of a sugar beet Waste liquor in a proportion to produce a mixture having a pH in the range of about 4 to about 6, concentrating and desalting the resulting mixture at a pH in said range, and combining the desalted mixture with said minor fraction in a proportion to produce a mixture having a pH around 3.2 for crystallization of glutamic acid therefrom.

2. A process as in claim l wherein said minor fraction comprises between about 40 and about 47.5% by volume of .the acid hydrolyzate.

3. A process for recovering glutamic acid lfrom a sugar beet waste liquor which comprises hydrolyzing a sugar beet waste liquor inthe presence of hydrochloric acid at a solids content between about 6G and about 85% by weight, separating insoluble material from the acid hydrolyzate, crystallizing betaine hydrochloride and glutamic acid hydrochloride from the insolubles-free acid hydrolyzate, separating the resulting slurry into a minor portion containing the crystallized solids and a major por-tion substantially free from said solids, said minor portion comprising between -about 40 and about 47.5% by volume of the acid hydrolyzate, hydrolyzing another portion of -a sugar beet Waste liquor under alkaline conditions, commingling the resulting alkaline hydrolyzate with said major portion of the acid hydrolyzate in a proportion to give a pH between about 4 and about 6, concentrating the resulting mixture to a solids content 'between about 65 and about 85% by weight, crystallizing and separating inorganic salts therefrom, comm-ingling the resulting liquid With a suiiicient quantity of said minor portion of the acid hydrolyzate to give a pH around 3.2, and crystallizing glutamic acid from the resulting solution.

4. A process as in claim 3 wherein said sugar beet waste liquor is Steifens filtrate.

5. A process as in claim 3 wherein said sugar beet waste liquor is barium ltrate.

6. A process as in claim 3 wherein said sugar beet waste liquor is a fermentation residue.

7. A process yas in claim 3 wherein said minor por-tion comprises .around 45% by volume of the acid hydrolyzate.

8. A process for recovering `glutamic acid from concentrated Steffens `filtrate which comprises hydrolyzing a portion of Stetfens filtrate by heating with hydrochloric acid at a pH of about 0 and a tempera-ture around the reflux point for labout 2 hours at a solids content of about -by Weight, separating humins from the resulting hydrolyzate, crystallizing betaine hydrochloride and glutamic acid hydrochloride from the humm-free acid hydrolyzate, separating the resul-ting slurry into a minor portion containing the crystallized solids and a major portion substantially free from said solids, said minor portion comprising about 45% Iby volume of the burnin-free acid hydrolyzate, hydrolyzing another portion of concentrated Steffens ltrate `by heating with sodium hydroxide solution Iat a solids content of about 65% by Weight, conimingling the `alkaline hydrolyzate with a suicient quantity of said major portion of the acid hydrolyzate to give a pH between about 4.5 and about 5.5, separa-ting insoluble material therefrom, concentrating the resulting liquid to a solids content of about 'by weight, crystallizin g and separating inorganic salts therefrom, adding to the resulting liquid a suicient quantity of said minor portion of the acid hydrolyzate to give la pH of about 3.2, and crystallizing glutamic acid from the resulting solution.

References Cited in the tile of this patent UNITED STATES PATENTS 2,788,368 Purvis Apr. 9, 1957 

1. IN A CO-NEUTRALIZATION PROCESS FOR RECOVERING GLUTAMIC ACID FROM SUGAR BEET WASTE LIQUORS, THE IMPROVEMENT WHICH COMPRISES CRYSTALLIZING BETAINE HYDROCHOLORIC AND GLUTAMIC ACID HYDROCHLORIDE FROM HYDROCHLORIC ACID HYDROLYZATE OF A CONCENTRATED SUGAR BEET WASTE LIQUOR, SEPARATING THE RESULTING SLURRY INTO A MINOR FRACTION CONTAINING THE CRYSTALLIZED SOLIDS AND A MINOR FRACTION SUBSTANTIALLY FREE FROM CRYSTALLIZED SOLIDS, COMBINING THE MAJOR FRACTION WITH ALKALINE HYDROLYZATE OF A SUGAR BEET WASTE LIQUOR IN A PROPORTION TO PRODUCE A MIXTURE HAVING A PH IN THE RANGE OF ABOUT 4 TO ABOUT 6, CONCENTRATING AND DESALTING THE RESULTING MIXTURE AT A PH IN SAID RANGE, AND COMBINING THE DESALTED MIXTURE WITH SAID MINOR FRACTION IN A PROPORTION TO PRODUCE A MIXTURE HAVING A PH AROUND 3.2 FOR CRYSTALLIZATION OF GLUTAMIC ACID THEREFROM. 